Method of making bimetallic articles



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' METHOD OF MAKING BIMETALLIC ARTICLES Original mm m 21. was v aSheets-Sheet 1 INVENTOR. Giokqz 7T L/wo THG .A

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' INVENTOR. 650x61: T. L000 July 7, 1959 'G. T; LADD v METHOD OF MAKINGBIMETALLIC ARTICLES Original Filed May 21, 1953 I 3 Sheets-Sheet 5 MIIIIZ INVENTOR. Giokqe Z L000 United States Patent METHOD OF MAKINGBTMETALLIC ARTICLES George T. Ladd, Huntington Station, N.Y., assignorto Fairchild Engine and Airplane Corporation, Farmingdale, N.Y., acorporation of Maryland Continuation of application Serial No. 356,572,May 21, ggSiMThis application August 10, 1956, Serial No.

2 Claims. (Cl. 22-204) This invention relates to a method of makingbimetallic articles, and has particular reference to a method of makinga bimetallic soleplate, although the method is not limited to makingsoleplates.

This is a continuation of application Serial No. 356,572, filed May 21,1953, now abandoned.

Following the development of lightweight flatirons, involving the use ofaluminum and its alloys, it soon became evident that the desirableattribute of lightness of aluminum is also accompanied by inherentdefects of the metal for that purpose, viz., softness, causing it toscratch and burr readily, discoloration due to steaming, particularly insteam irons, and surface porosity which usually becomes evident onlyafter the sole of the iron has been polished. Electroplating thealuminum sole or fusing it to a copper or other metallic face plate haveproved costly and require considerable machining and other finishing,especially the latter, because of thermal warping and incomplete unionbetween the aluminum and the face plate.

In accordance with the present invention, a method of making surfacehard castings, such as a bimetallic soleplate for flatirons is provided,whereby a very thin and therefore flexible sheet of highly polished orpolishable metal harder than aluminum, such as stainless steel, isuniformly bonded to the aluminum body of the plate to afford alightweight iron having a hard and a truly fiat ironing surface,notwithstanding the initial flexibility of the sheet.

In a preferred mode of conducting the process of this invention, thestainless steel sheet, on the order of between one and two hundredths ofan inch thick, is precoated with molten aluminum at a temperature toform a ferro-aluminum alloy thereon, placed in a plane-bottomed cavityof the cover of a pressure die casting or permanent mold having thefacing cavity shaped to the dimensions of the aluminum portion of thebimetallic unit to be formed, the mold closed and molten aluminum forcedtherein at a sufficient pressure to flatten the steel sheet against theplane surface of the cover die to become truly flat as the aluminum isfused to the still plastic aluminum-coated surface of the sheet andcongeals to complete the sole-plate which may have the heating unitinserts cast therein in the same pressure casting operation. Instead ofimmediately casting the aluminum against the aluminum predipped sheetwhile the aluminum thereon is still molten or plastic, the aluminumcoating on the sheet may be reactivated by reheating the same while thesheet is seated in the cover cavity and immediately before the pressurecasting operation. The steel sheet may be preformed with steam nozzlerecesses and the like, with the mold cover cavity formed with matingbosses to afford the shaping support for the sheet during the pressurecasting step.

It will be seen that the method of this invention affords a simple,accurate and inexpensive way of producing numerous bimetallic articleshaving the advantages of lightness of the light but soft metals, and thehardness and smoothness advantages of cast steel without its weight.

For a more complete understanding of the invention, reference may be hadto the accompanying drawings, in which:

Figure 1 is a longitudinal section through the flatiron soleplate, madeaccording to the method of this invention, and showing the outline of asteam iron to which the invention may be adapted;

Fig. 2 illustrates a dished stamping of the sheet of stainless steel orthe like, intended to serve as the ironing surface of the finished iron;

Fig. 3 shows in a semi-schematic way the two parts of a pressuredie-casting or permanent mold having the sheet stamping of Fig. 2 seatedin the cover die cavity provided therefor and the facing moldpreparatory to closing the same for pressure injection of the castingaluminum therein; and

Fig. 4 is a similar semi-schematic view of the open die with a gas-firedburner interposed between them for heating the aluminum precoatedsurface of the sheet stamping to reactivate the same preparatory to thepressure casting step.

The sheet metal to be used as the surfacing material for the soleplateis on the order of about .006 to about .030 inch thickness andpreferably is one of the stainless steels, including the austenitic,martensitic and ferritic series and the like, or the sheet may be of lowcarbon steel and preplated on its ironing surface with chromium ornickel before the casting operation or thereafter. According to theinvention, this thin sheet metal becomes part 12 of the finishedbimetallic soleplate of the iron as shown in Fig. 1, the other partbeing the aluminum casting 11. The metal sheet 12 is in the form of astamping and comprises the recessed soleplate surface portion 13 havingthe contour of the finished soleplate and the die-sealing flange 14extending around its perimeter as shown especially in Fig. 2. If thefinished fiatiron is to be of the dry type, the surface portion 13 isuninterrupted, but if it is to be a steam iron, the interior boss 15 orthe like, may be provided and subsequently perforated at 16, as shown inFig. 1.

The stamping 12 is adapted to be seated in the carefully machined recess17 provided therefor in the cover die 18 of a pressure die-casting orpermanent mold comprising two halves or frames 19 and 20 adapted to bebrought and clamped together into juxtaposition by known means tojointly form the mold cavity one half of which is constituted by therecessed portion of the stamping 12, and the other half by the cavity 21in the die 22, carried by frame 20, as shown in Fig. 3.

As stated, the recess in die 18 is carefully machined, so that thebottom of the recess 17 which the ironing surface portion of stamping 12is adapted to overlie is perfectly flat and true, except for thatportion supporting the boss 15. To preclude distortion of the perimeterof the stamping 12, the die is similarly accurately machined to closelyaccommodate the die sealing flange 14. A pin 23 in die 18 assists inaccurately locating the stamping 12 thereon by passing through a hole 24in its flange 14 and seating in a socket 25 in die 22.

The cavity 21 of die 22 is shaped to form with the inner surface ofstamping 12 the aluminum portion 11 of the soleplate 10, including theprojection 26 cooperating with boss 15 to form the steam chamber 27shown in Fig. 1. If desired, the die 22 may be so shaped as toaccommodate the electrical resistance heating socket and the like, thatare to be cast into the aluminum in accordance with known practice. gThe casting aluminum ingate 27 between the die cavity 21 and the.cylinder 28 is formed in the die 22 and its frame 20 and cylinder 28 issupplied with molten alur 3 minum through spru'e 29 which is forced bypiston 30 into the closed die cavity in the known manner.

In carrying out the method of making bimetallic articles according tothe present invention, particularly in the manufacture of bimetallicsol'e pla't'es for flatirons, it is first necessary to prepare the innersurface of the stamping 12 for bonding with the casting aluminum oraluminum alloy through the intermediary film ofja ferro;

aluminum alloy at the interface between the steel and about 15,000pounds per square, inch. At pressures of this order, the thin flexiblesheet metalof which stamping 12 is formed is forced coextensivelyagainst the bottom of the die 18 to conform to the true surface thereof.Notwithstanding the; inherently flimsy nature of the very thin stamping12, it becomes true under casting pressure and remains true as thealuminum freezes and fused with the aluminum coating overlying theferroaluminum alloy film to become the unitary bimetallic soleplate 11of Fig. 1, subject to trimming off the flange ltand drilling the steamjet holes 16.

Instead ofcasting immediately after application of the forte-aluminumalloy film to the inner surface and while the overlying aluminum layeris still molten or plastic, as .described, the stampling 12 may bepretreated to provide the ferro-aluminum film, allowed to cool and thenreactivated at any subsequent time by heat-softening the overlyingaluminum coating immediately before casting, preferably after theprecoated stamping has been seated recess in the die 18.

, Referring to Fig. 4, the prebonded stamping 12 in the cold state,having been treated either before or after stamping from a sheet of thinstainless steel or the like, is seated in its recess in its cavity indie 18 while'the frames 1-9 and 20 are open and-spread apart, Then amultiple oxyacetylene orother gas-fired burner 30 is suspended inproximity to thevprebonded inner surface of stamping 12 and the latterheated toa temperature on the order of 1300" to 1450" F tomelt or renderplastic the thin residual of'.001, to .003 inch layer of aluminumoverlying the ferro-aluminum alloyfilm. It appears that notwithstandingits aluminum oxide surface, the aluminum surface layer is softened andsubdivided sufliciently by thisreheating' operation that when the moldis closed and'the aluminum injected at the aforementioned pressure, thealuminum oxide is'fiushed away and dissipated throughout the body ofaluminum. Microscopic examination shows no discernible differencebetween a reactivated bond and one that is formed while the initialaluminum overcoat is still molten or plastic, nor is the ferro-aluminumfilm affected or difierent by reason of such reactivation.

The burner. 30 may comprisea steel shell 31 fitted with a ceramic liner32' having a flame chamber 33 of the contour of the stamping, l2 andprovided with a plurality of jet nozzles 34icommunicating with a gasmanifold 35 supplied with oxyacetylene or other fuel gas mixture from asuitable pressure-source byfi'exible tube 36. As indicated in Fig. 4,burner 30-may be lowered and raised into and out of operationalalignment with stamping 12.

'It will be evident that-the process ofthisinvention is useful in theformation-of-binietallic-articlesfor vari' ous 'uses, wherein a thinlayer of one-metal is desired to serve as a wearing, bea r mg,ornamental-or other surface overlying a body of compatible metal capableof being cast at sufiiciently high pressures to hydraulically flatten orotherwise shape the thin sheet metal against and in conformance with thecontour of a die affording the requisite shape. Thus, in addition toaluminum and its alloys, magnesium and, its alloys, titanium and itsalloys, copper and itsalloys, nickel and its alloys, and the like, mayserve as the casting metal to pressure shape and be permanently unitedthrough an alloy bond; to; one surface of a thin sheet of a diflerentmetal adding desired properties to the surface of the casting which thecasting metal does not possess.

Atthough hydraulic pressure-conforming union of very thin ferrous metalalloy sheet to aluminum or aluminum base alloys through the intermediaryof a ferro-aluminum alloy bond has been particularly described, verythin sheets of non-ferrous metals immediately compatible with moltenaluminum by alloying therewith may also be united thereto according tothe invention. Among such compatible non-ferrous metals are silver,copper, nickel, chromium, titanium, molybdenum, tantalum, andthe alloysthereof, such as theMonel series, as well as the nimonic series, thebrasses, bronzes, and the like. Sheet made of these metals or alloys, orferrous metal, sheet coated or plated therewith or with a suitablebrazing, t-inning, galvanizing, or soldering metals or alloys may. beunited with the casting metal in the manner described withoutpretreatment except cleansing or fluxing where necessary. Accordingly,many cast articles including flatiron soleplates, pressing machineshoes, calendering rolls, and the like, may be surfaced with very thinsheet metal by means of the hydraulic pressure-conforming process ofthis invention.

Although certain preferred embodiments of the invention have beenillustrated and described herein, it is to be understood that theinvention is not limited thereby, but is susceptible of changes in formand detail within the scope of the appended claims in which the termaluminous metal means aluminum and aluminum base alloys.

I claim:

1. The method ofproviding a casting of an aluminum base metal with asurface coating of a harder, denser, polishable ferrous metal,comprising bonding with a sheet of flexible ferrous metal having athickness between about @006 and about .030 inch, a surface film of themolten aluminum base metal by means of an interposed thin layer of aferro-aluminum alloy, allowing the sheet to cool to solidify the surfacefilm thereon and consequently form an oxide'surface skin on said surfacefilm, mounting the cooled sheet in a mold having a contour desired forthe surface of the finished casting, heating the surface film to meltthe same, closing the mold, injecting molten aluminum base metal intothe mold at high velocity to flush the oxide skin from the moltensurface film to expose the same, said molten aluminum base metal beingsubjected to a pressure between about 4,000 and 15,000 psi to force saidsheet into coextensive engagement with said mold and being maintained'ata temperature to fuse with the exposed surface film of molten metalon-said sheet, maintaining said pressure within the mold until thecasting metal has solidified, and removing the resulting bimetalliccasting from the mold.

2. The method of providing a casting of an aluminum base metal with asurface layer of a harder, denser, polishable metal, comprising mountingin a moldhaving a contour desired forthe surface of the finishedcasting, a sheet'of polishable ferrous metal between about .006 andabout .030 inch inthickness and having a solidified surface film of analuminum base metal bonded to it by an interposed film of aferro-aluminum alloy, said surfacefilm having an oxide skin thereon,heating the sheet to meltthe surface film of aluminum basemetal, closingthemold, injecting moltenaluminumbase metal into the mold at highvelocity, to flush the oxide skin from. the

molten surface film to expose the same, said molten metals and sheet offerrous metal being subjected to a pressure between about 4,000 and15,000 p.s.i. to force said sheet into co-extensive engagement with saidmold and being maintained at a temperature to fuse the injected metalwith the surface film of molten aluminum base metal on said sheet,maintaining said pressure within the mold until the aluminum base metalhas solidified, and removing the resulting bimetallic casting from themold.

References Cited in the file of this patent UNITED STATES PATENTS915,021 Dunton Mar. 9, 1909 6 White May 7, 1935 Sansome Feb. 22, 1938Whitfield Mar. 19, 1946 Myers Apr. 11, 1950 Grange et a1. Mar. 13, 1951Brennan Sept. 25, 1951 Jung July 28, 1953 Tanner June 29, 1954 BrennanSept. 18, 1956 Whitfield July 2, 1957 FOREIGN PATENTS Great Britain June25, 1931 Great Britain Mar. 22, 1950

1. THE METHOD OF PROVIDING A CASTING OF A ALUMINUM BASE METAL WITH ASURFACE COATING OF A HARDER,M DENSER, POLISHABLE FERROUS METAL,COMPRISING BONDING WITH A SHEET OF FLEXIBLE FERROUS METAL HAVING ATHICKNESS BETWEEN ABOUT .006 AND ABOUT .030 INCH, A SURFACE FILM OF THEMOLTEN ALUMINUM BASE METAL BY MEANS OF A INTERPOSED THIN LAYER OF AFERRO-ALUMINUM ALLOY, ALLOWING THE SHEET TO COOL TO SOLIDIFY THE SURFACEFILM THEREON AND CONSEQUENTLY FORM AN OXIDE SURFACE SKIN ON SAID SURFACEFILM, MOUNTING THE COOLED SHEET IN A MOLD HAVING A CONTOUR DESIRED FORTHE SURFACE OF THE FINISHED CASTING, HEATING THE SURFACE FILM TO MELTTHE SAME, CLOSING THE MOLD, INJECTING MOLTEN ALUMINUM BASE METAL INTOTAHE MOLD AT HIGH VELOCITY TO FLUSH THE OXIDE SKIN FROM THE MOLTENSURFACE FILM TO EXPOSE THE SAME, SAID MOLTEN ALUMINUM BASE METAL